Structure of the O-acetylserine sulfhydrylase isoenzyme CysM from Escherichia coli |
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Authors: | Claus Michael T Zocher Georg E Maier Thomas H P Schulz Georg E |
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Affiliation: | Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universit?t, Albertstrasse 21, D-79104 Freiburg im Breisgau, Germany. |
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Abstract: | The enzyme O-acetylserine sulfhydrylase participates in the biosynthesis of l-cysteine in bacteria and plants. The structure of isoenzyme B (CysM) from Escherichia coli was established in a hexagonal crystal form at 2.7 A resolution (wild-type) and in a merohedrally twinned tetragonal crystal form at 2.1 A resolution (surface mutant). Structural superpositions revealed the variations with respect to isoenzyme A (CysK) and explained the different substrate specificities. A geometric model of the reaction catalyzed by CysM is proposed. Both isoenzymes are used for the production of l-amino acid derivatives as building blocks for the synthesis of peptides and peptidomimetic drugs. Since the structure of CysM revealed a remarkable main chain variation at the active center, it constitutes a further starting point for engineering mutants with novel substrate specificities. |
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